Not sure which DB rails is using

I am very new to rails and web apps in general, please bardon me if the question is very basic.

I am working on a rails app, where I have created users with scaffolding and saved some entries through the browser. It seems to be doing everything correctly.

The problem is I am not sure which database the app is using. I have mysql but no changes are happening there. Is rails using sqlite instead? If so, how can I switch to mysql or another db

thanks